1. Technical Field
The subject matter of this disclosure generally relates to the field of medical devices. More specifically, the present disclosure relates to non-surgically implantable medical devices and methods for implementing vagus nerve therapy.
2. Background Information
Many advancements have been made in treating medical conditions involving or mediated by the neurological systems and structures of the human body. In addition to drugs and surgical intervention, therapies using electrical signals for modulating the electrical activity of the body have been found to be effective. In particular, medical devices have been effectively used to deliver therapeutic electrical signals to various portions of a patient's body (e.g., the vagus nerve) for treating a variety of medical conditions. Electrical signal therapy may be applied to a target portion of the body by an implantable medical device (IMD) that is located inside the patient's body or, alternatively, may be applied by devices located external to the body. In addition, some proposed devices include a combination of implanted and external components.
The use of medical devices to provide electrical signal therapy has increased rapidly in recent decades. Such devices include pacemakers and defibrillators, which provide electrical signal therapy to heart tissue, as well as spinal cord stimulators for treatment of pain. In addition, devices have also been approved to provide electrical signal therapy to the vagus nerve (the 10th cranial nerve) to treat epilepsy and depression. Additional medical devices for providing electrical signal therapy have been proposed for stimulation of other nerves, such as the sympathetic nerve, the phrenic nerve and the occipital nerve.
The vagus nerve (cranial nerve X) is the longest nerve in the human body. It originates in the brainstem and extends, through the jugular foramen, down below the head, to the abdomen. Branches of the vagus nerve innervate various organs of the body, including the heart, the stomach, the lungs, the kidneys, the pancreas, and the liver. In view of the vagus nerve's many functions, a medical device such as an electrical signal generator has been coupled to a patient's vagus nerve to treat a number of medical conditions. In particular, electrical signal therapy for the vagus nerve, often referred to as vagus nerve stimulation (VNS), has been approved in the United States and elsewhere to treat epilepsy and depression. Application of an electrical signal to the vagus nerve is thought to affect some of its connections to areas in the brain that are prone to seizure activity. Because of the vagus nerve's innervation of the stomach, stimulating the vagus nerve may also be therapeutically beneficial to treating eating disorders such as bulimia nervosa, as well as treating morbid obesity.
Current and proposed VNS treatments have involved surgically coupling electrodes to the left and/or right vagus nerves in the neck. Other treatments involve surgically implanting electrodes to one or more surfaces in the abdomen, such as by laparoscopic surgery through the patient's abdominal wall. Electrical signal therapies in addition to VNS have been proposed to treat eating disorders such as obesity. These techniques include coupling electrodes to the exterior and/or interior of the stomach, duodenum, or intestinal walls. However, all of the aforementioned therapies either do not provide stimulation directed specifically to the vagus nerve, substantially interfere with normal gastrointestinal function, require some type of invasive surgery, or all of the above.
Consequently, there is a need for non-surgical devices and methods for treating medical conditions. There is also a need for providing an easily implanted device that provides little or no interference with normal gastrointestinal function. There is also a need to provide improved methods and devices for vagus nerve stimulation, and to avoid undesired side effects associated with conventional surgical vagus nerve stimulation.